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to the base of the prostate. The posterior surface rests upon the rectum, from which it is separated by the rectovesical fascia. The upper extremities of the two vesicles diverge from each other, and are in relation with the ductus deferentes and the terminations of the ureters, and are partly covered by peritoneum. The lower extremities are pointed, and converge toward the base of the prostate, where each joins with the corresponding ductus deferens to form the ejaculatory duct. Along the medial margin of each vesicle runs the ampulla of the ductus deferens.

Each vesicle consists of a single tube, coiled upon itself, and giving off several irregular cecal diverticula; the separate coils, as well as the diverticula, are connected together by fibrous tissue. When uncoiled, the tube is about the diameter of a quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac; its anterior extremity becomes constricted into a narrow straight duct, which joins with the corresponding ductus deferens to form the ejaculatory duct.

Structure.—The vesiculæ seminales are composed of three coats: an external or areolar coat; a middle or muscular coat thinner than in the ductus deferens and arranged in two layers, an outer longitudinal and inner circular; an internal or mucous coat, which is pale, of a whitish brown color, and presents a delicate reticular structure. The epithelium is columnar, and in the diverticula goblet cells are present, the secretion of which increases the bulk of the seminal fluid.

Vessels and Nerves.—The arteries supplying the vesiculæ seminales are derived from the middle and inferior vesical and middle hemorrhoidal. The veins and lymphatics accompany the arteries. The nerves are derived from the pelvic plexuses.

3c. 4. The Ejaculatory Ducts

(Ductus Ejaculatorii)

The ejaculatory ducts (Fig. 1153) are two in number, one on either side of the middle line. Each is formed by the union of the duct from the vesicula seminalis with the ductus deferens, and is about 2 cm. long. They commence at the base of the prostate, and run forward and downward between its middle and lateral lobes, and along the sides of the prostatic utricle, to end by separate slit-like orifices close to or just within the margins of the utricle. The ducts diminish in size, and also converge, toward their terminations.

Structure.—The coats of the ejaculatory ducts are extremely thin. They are: an outer fibrous layer, which is almost entirely lost after the entrance of the ducts into the prostate; a layer of muscular fibers consisting of a thin outer circular, and an inner longitudinal, layer; and mucous membrane.

FIG. 1153– Vesiculæ seminales and ampullæ of ductus deferentes, seen from the front. The anterior walls of the left ampulla, left seminal vesicle, and prostatic urethra have been cut away. (See enlarged image)

3c. 5. The Penis

The penis is a pendulous organ suspended from the front and sides of the pubic arch and containing the greater part of the urethra. In the flaccid condition it is cylindrical in shape, but when erect assumes the form of a triangular prism with rounded angles, one side of the prism forming the dorsum. It is composed of three cylindrical masses of cavernous tissue bound together by fibrous tissue and covered with skin. Two of the masses are lateral, and are known as the corpora cavernosa penis; the third is median, and is termed the corpus cavernosum urethræ (Figs. 1154, 1155).

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